In 1935, Claude S. Beck recommended ligation of the coronary sinus as part of an operation to imprve myocardial blood supply. In the present studies this procedure was evaluated by modern methods for measurement of total and regional myocardial perfusion and left ventricular performance. Coronary sinus ligation acutely decreases total LV perfusion, but, due to flow redistribution, the subendocardium is spared. In fact, after 30 min. the favorable flow redistribution to the subendocardium continues, at a time when LV perfusion returns to normal. It may be possible to improve blood flow to the subendocardium by elevating pressure in the coronary sinus.